An organic light-emitting diode (OLED) is bright in color, high in luminous efficiency, light in weight, wide in view angle, fast in response speed, and available from flexible preparation, and thus belongs to a new generation display technology following after LCD (Liquid Crystal Display). Unlike an LCD which needs a thick backlight, and thus has great visibility and high brightness, an OLED is featured by autoluminescence. According to drive modes, OLEDs can be classified into PMOLED (Passive Matrix Organic Light Emitting Diode) and AMOLED (Active Matrix Organic Light Emitting Diode). It is easier for an AMOLED to realize a high brightness and a high resolution because there is no problem of a duty ratio and no limitation on the number of scan electrodes for driving the same.
Generally, resolution of AMOLED mainly depends on precision of a mask used for evaporation of organic light-emitting material in the manufacturing process of OLED, where an FMM (Fine Metal Mask) is typically used as the mask. As electronic equipment is demanding for high resolution and high brightness of display screens, the area of a single pixel is gradually decreased, and the distance between sub-pixels having the same color is reduced accordingly. Higher requirements are put forward for the precision of FMM required by evaporation of OLED if a traditional arrangement mode of pixels in LCD is stilled adopted. When the distance between sub-pixels having the same color is reduced, the spacing between mesh openings on FMM is decreased accordingly. However, relatively great technical difficulties exist in fabricating FMM with extremely small spacing between mesh openings due to limitation by characteristics of raw materials.
An AMOLED consists of multiple pixel units arranged in array, and a schematic diagram illustrating such pixel structure according to an exemplary embodiment is as shown in FIG. 1. Each pixel unit includes a red (R) sub-pixel, a green (G) sub-pixel and a blue (B) sub-pixel. Each pixel unit needs one corresponding pixel driving unit to drive it. Brightness of an OLED in each sub-pixel is controlled by a driving subunit. As shown in FIG. 2, which is a schematic diagram illustrating a pixel unit in a pixel structure driven by a pixel driving unit in a pixel driving circuit, three sub-pixels in the pixel unit are respectively driven by three driving subunits 01, 02 and 03. Therefore, each pixel unit needs three driving subunits to drive it to implement color mixing of various pixels. Further, each driving subunit at least consists of a storage capacitor, a drive transistor and at least one switch transistor. Taking a typical 2T1C pixel drive circuit consists of TFTs (Thin Film Transistor) as an example, the schematic diagram illustrating an equivalent circuit of a 2T1C driving subunit is as shown in FIG. 3. In FIG. 3, MS is a switch transistor configured to control input of data line voltage; a grid electrode of MS is connected to a scanning line Sn, a source electrode or a drain electrode of MS is connected to a data line Data. MD is a drive transistor configured to control luminescence current of the OLED. CS is a storage capacitor configured to provide bias voltage and maintaining voltage for the grid electrode of the drive transistor MD, which can play a role in continuous power supply and ensuring continuous luminescence of various pixels. ELVDD is operating voltage, ELVSS is source voltage, and IOLED is working current of the drive transistor MD.
As electronic equipment is in pursuit of high resolution and high brightness of the display screen, the area of a single pixel is gradually decreased, and the distance between sub-pixels having the same color is reduced accordingly. In view of difficulties in fabricating an FMM screen and diffusion of organic light-emitting materials in evaporation process of OLED, higher requirements are put forward for FMM required by evaporation of the OLED since certain difficulties exist in achieving closely adjacent strip-shaped OLED sub-pixels having the same color as shown in FIG. 1. On the other hand, the gradually decreased area of pixel may impose restriction on design and layout of a driving circuit in the backplate due to limitation by precision of etching process.
Therefore, certain difficulties exist in achieving closely adjacent strip-shaped sub-pixels having the same color due to limitations of difficulties in fabricating the mask and of the process in evaporation procedure, thereby restricting an arrangement mode of OLED pixels.
The foregoing information is merely disclosed to facilitate understanding of background of the present disclosure. Therefore, the foregoing information may include information not constituting the prior art known to those of ordinary skill in the art.